Our experiment was concerned with the reflex response in humans, and how it compares to a voluntary neural pathway as well as how it is enhanced by what is known as the Jendrassik Maneuver. Our hypothesis was that the reflex response would be faster than the voluntary response, and that with the Jendrassik maneuver, the reflex would be even more responsive. We predicted the latency to be lower for the reflex as compared to the voluntary response, and the amplitude to be higher for the reflex with the Jendrassik maneuver as compared to the reflex on its own. We conducted this experiment with the help of an apparatus that measured the angle during leg movement after the reflex. Specifically, flexion of the quadriceps (the reflex response) would cause the leg to kick out. The apparatus was basically two pieces of plastic connected to each other at a joint. One piece was attached to the calf and the other to the thigh. When the leg kicked out, the angle at which the two pieces of plastic connected changed, and the magnitude of change was recorded on a computer hooked up to the device. It would serve well to understand some background information about the neuron, neurotransmitters and their receptors, excitatory/inhibitory reflexes, and involuntary reflexes.
[...] Again using acetylcholine as an example, it can act as an excitatory neurotransmitter in the neuromuscular junction to stimulate muscle movement, but it can also act as an inhibitory signal in the parasympathetic nervous system causing heart rate to slow down. Its action depends on the kind of receptor it binds to (Campbell and Reece, 1014-1024). Although many actions are voluntary, some are not. The knee jerk reflex tested in this experiment was one such involuntary movement. This reflex never passed through the brain, and thus is not consciously controlled. Its pathway is somewhat different. [...]
[...] the reflex knee jerk, our predictions also held up. It is evident in the tables that the average latency for the voluntary response was higher than the average latency for the reflex response. This indicates that the time for the action of knee jerking to be carried out took longer with the voluntary response. The reason for this is that for the voluntary response, the signal must be integrated in the brain, and must then be sent out through motor neurons to the muscle to elicit the response. [...]
[...] The Jendrassik did indeed increase the reflex response, as can be seen by the higher average amplitude in the tables. The responses fluctuated, but the average still came out higher. Fluctuation was likely caused by the fact that not every hit was perfectly on the tendon. Some hits elicited lower responses if the tendon was not hit directly, and higher if the tendon was hit directly and with more force. It is also interesting to note that the average latency for the Jendrassik response was lower than the normal reflex. [...]
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